Here is a fun creature creator, Spore 2D http://www.spore2d.com/
It is derived from the Spore game but is simply the creature creator and easy to use. Students can create a creature of their choice. This can be used as stimulus for a writing task, comics, art work or students could decide the habitat in which it would live.
You can save your final creature to a file on your computer as a .png file.